The movement of proteins over ˜40 kDa into and out of the nucleus is governed by the nuclear pore complex (NPC), a multi subunit structure embedded in the nuclear envelope (Jans et al., 2000). Transcription factors and enzymes that regulate the activity of these proteins are shuttled across the nuclear envelope by proteins that recognize nuclear localization signals/sequences (NLS) and nuclear export signals (NES). Positively charged NLSs are bound by importins α and/or β—also known as karyopherins—which tether cargo to the cytosolic face of the nuclear pore complex and facilitate translocation of proteins into the nucleus. The CRM1 protein, also referred to as exportin, mediates the transfer of proteins out of the nucleus (Fornerod et al., 1997), although CRM1-independent mechanisms for nuclear export exist (Kutay et al., 1997). The ability of nuclear import and export machinery to access a NLS or NES is often dictated by signalling events that lead to the exposure or masking of these regulatory sequences (Cyert, 2001). This may occur through direct modification of the target protein or via modification of an associated factor.
The signalling cascade of calcineurin (CnA) and the nuclear factor of activated T cells (NF-ATc) is a crucial transducer of cellular function. NF-ATc is an ubiquitous transcription factor but has particular relevance in cytokine expression and the development of pathologic myocardial hypertrophy. The formation of complexes between transcription factors and DNA is crucial for the transcriptional process. Therefore, the time that transcription factors remain nuclear is a major determinant for transcriptional activity. It was shown that that in addition to the transcription factor NF-ATc, the phosphatase calcineurin is also translocated to the nucleus (Burkhard et al., 2005; Frey et al., 2000; Zou et al., 2001; Shibasaki et al., 1996). Calcineurin is therefore not only responsible for dephosphorylating NF-ATc, thus enabling its nuclear import; its presence in the nucleus is also significant in ensuring the full transcriptional activity of NF-ATc (Zhu et al., 1999). The traditional understanding of calcineurin activation via sustained high Ca2+-levels (Timmerman et al., 1996; Dolmetsch et al., 1997) was advanced by findings of the inventor that calcineurin is activated by proteolysis of the C-terminal auto-inhibitory domain, which leads to a constitutively nuclear translocation of calcineurin (Burkhard et al., 2005).
Calcineurin is known to suppress the immune system, and various pharmaceutical compositions are available from commercial sources. Calcineurin inhibitors belong to the group of cyclosporine, tacrolimus (Protopic®, Prograf®) and pimecrolimus. Indications are psoriasis, atopic dermatitis, rheumatism and allergies, to name a few.
US patent application No. 2003/0045679 A1 to Crawford describes compositions which are useful for inhibiting and potentiating the activity of cellular calcineurin. These compositions include peptides, peptide analogs and whole proteins. They can be used to treat calcineurin related pathologies such as cardiac, brain, immune system and developmental abnormalities.
All known calcineurin inhibitors show strong side effects like high blood pressure, renal disorders and viral and bacterial infections. The later two are due to their general immunosuppressive properties. Thus there is a still existing need for a pharmaceutical composition for the treatment of calcineurin related disorders, like myocardial disorders, psoriasis, rheumatism, immune reactions and suppression, e.g. graft versus host reaction and transplant rejection; allergies, asthma, in particular cardiac asthma, bronchial asthma and allergic asthma.
The solution to this problem is achieved by providing the embodiments characterized by the claims, and described further below.